We cycle as a family. A lot. Some years I cycle further than I travel by car. So, this is something we've really thought about!
It depends on what sort of bikes (you've listed those) and whether you need to be able to get each one out without moving another. Dbro hangs all his, he has a lot (maybe 12?) but he's strong, and I'm not - his are suspended by the front wheel; I absolutely couldn't do that. Plus mine has a basket, which I use every day (so non-negotiable).
We have ours leaning along the walls of the garage, plus two leaning against the BBQ (which doesn't get much use!). Leaning against a wall means mine is properly stable (otherwise the front wheel moves around and the whole thing tips; a joy when using racks).
In a previous house we had to keep them in the living room, and while we still used them every day, it was a faff. I can't overstate how much easier my life is for being able to wheel straight out of the garage, and not untangle my bike from DH's and lift it over a step.
Topping and tailing will only really work if some of the bikes are used a lot less; I've had to lift my handlebars over another bike before, and it isn't great. I think the space you've described will be tight (also, where will the trailer go?). I'd go for as big as possible - you won't regret it!